Evidence for molecular tungsten ionic species presence in impurity-seeded hydrogen plasma in contact with W surfaces

Abstract

We performed an investigation of tungsten ionic species presence in hydrogen plasmas in contact with a tungsten surface, both in the presence of air impurities and when injected with argon. The study was carried out in a magnetron sputtering system complemented with mass spectrometry diagnostics. Our findings reveal that these plasmas encompass a diverse range of tungsten molecular ionic species in the mass range of 180–250 amu, broadly described as WH_xN_yO_z⁺ (x = 0–3; y = 0–2; z = 0–3). The validity of these results was further confirmed through dedicated mass spectrometry investigations involving tungsten sputtering discharges in argon–nitrogen and argon–oxygen mixtures.